1. Field of the Invention
The invention is concerned with preventing the discharge of copper resulting from the degration of isothiazolone biocides into industrial waste water streams.
2. Description of the Prior Art
Isothiazolone biocides are used to treat a variety of industrial process waters such as cooling tower waters, refinery process waters and the like to control the growth of microorganisms. They are also used extensively in treating paper mill process waters.
Aqueous solutions of isothiazolone biocides tend to break down under conditions of long term storage. To control this decomposition, manufacturers add copper ion in the form of a water soluble cupric salt, such as cupric nitrate, as a stabilizing agent. The amount of copper ion present in the isothiazolone solutions typically is between 0.1 to 0.2% by weight. In certain instances the isothiazolones contain small amounts of magnesium compounds, which are a manufacturing residue.
These process waters eventually become part of industrial waste water streams. Copper is deemed by most environmental regulations to be an undesirable pollutant in waste water streams, even if present in small quantities. The copper-stabilized isothiazolone biocides present in industrial process waters could add copper ion to the waste streams in potentially unacceptable amounts.
If it were possible to treat industrial process waters with copper-stabilized isothiazolone biocides whereby copper ion formed from these isothiazolone would not be added to the waste streams an advance in the art would be afforded. It would also be advantageous for the prevention of magnesium ions contained in isothiazolone biocides from contaminating waste water streams.